There are many types of hydraulic oils due to the number of applications in which hydraulics are used. Generally, they can be classified as shown in Figure 2.
There isn’t just one type of hydraulic oil. Depending on the application, different standards are associated with each type. The two main groups are hydrostatic applications and hydrodynamic/hydrokinetic applications.
The hydrodynamic applications mainly include ATFs (Automatic Transmission Fluids).
On the other hand, for the hydrostatic applications, the mobile systems refer to UTTO (Universal Tractor Transmission Oil) and STUO (Super Tractor Universal Oil).
These hydrostatic applications can be further categorized into mineral oil-based hydraulic fluids, fire-resistant hydraulic fluids, environmentally acceptable hydraulic fluids, and food-grade lubricants. Each of these has its associated standards and regulations.
For Mineral oil-based hydraulic fluids, there are different classifications, as shown in Figure 3 below.
For fire-resistant oils, their classifications include those shown in Figure 4 below.
For Environmentally Acceptable lubricants (particularly water-free, rapidly biodegradable hydraulic fluids), their classifications are shown in Figure 5 below.
For food-grade lubricants, their classifications include:
- NSF H1 – These are colorless, odorless, tasteless, non-toxic, and are certified for incidental contact with food
- NSF H2 – These are lubricants that can be used in food processing, but only where there is no contact with food.
(Other categories of NSF grades exist, but these do not apply directly to hydraulic oils.)
